Coordination polymers with varying dimensionality constructed from 2,5-bis(imidazol-1-yl)thiophene (thim2) and divalent metal (Mn2+, Cd2+, Co2+) salts

Abstract

The reaction of the angular tritopic ligand 2,5-bis(imidazol-1-yl)thiophene (thim2) with divalent metal salts [metal=Mn(II), Cd(II), Co(II)] containing different anions led to the formation of structures with different dimensionalities. In the case of manganese and cadmium nitrates, the 1D double chain CPs [Mn(thim2)2(NO3)2]n (1) and {[Cd(thim2)2(NO3)2]·(H2O)}n (2) were obtained, whereas two different products, viz. 2D+2D=3D polycatenated {[Co(thim2)2(H2O)2]·(NO3)2}n (3) and 2D parallel interpenetrated {[Co(thim2)2(NO3)2]n (4) networks, were synthesized with cobalt nitrate in different crystallization solvents using the same methodology. The use of manganese and cadmium acetates gave isostructural 1D double chain {[M(thim2)2(OOCCH3)2]·(H2O)}n [M=Mn (5); Cd (6)] CPs. However, cobalt acetate forms a 2D helical square grid framework, {[Co(thim2)2(OOCCH3)2]·(H2O)2}n (7). In addition to the effect of the anions, the role of the thim2 ligand conformations as well as the dihedral angle has been studied with regards to the structural variations. The thermal stabilities of 1–7 and photoluminescence properties of 2 and 6 were also investigated.